TheFont, custom motorcycle tech


Build your own Tube Bender



I want to talk about Ford Fiestas. Yes, the small hatchback thingy with four wheels. Specifically, the ones between the J and N registration marks.


What's so great about these Fiestas? Well it turns out that the rear stub axle is held on by four bolts, and that the rear drum has, roughly speaking, a four inch radius. Four inches is by a fortunate coincidence about the radius that you want for bends in a motorcycle frame.


One of the most elusive pieces of equipment you'll need for building or modifying frames is a tube bender. The hydraulic ones you see in tool supermarkets are in fact pipe benders and don't do a very good job of bending tube. So I made one out of a Fiesta rear stub axle and hub and it seems to do a much better job of bending tube and shouldn't cost more than 50 at the outside.



Fig.1
This model of Fiesta

So to paraphrase the words of the immortal Mrs. Beeton, first catch your Fiesta. Remove one of the rear wheels, and then take the cap off of the centre of the brake drum and undo the nut that holds the drum/hub on and remove that keeping in mind that the left side one has a left hand thread. Behind the brake back plate there are four bolts that attach the stub axle to the beam, once these are undone you can remove the stub axle and leave the brake back plate on the car. You need the stub axle, the drum/hub, the stub axle mounting bolts, the drum/hub retaining nut and cover, and at least two of the wheel nuts. This bender should work for 1", 1 1/8", and 1 " outside diameter tube, but you'll need to make a former and slider for each size so it might pay to grab the other hub while you're there.


Fig.2
The hub and stub axle

Materials you need are about 14 feet of 40mm by 80mm by 3mm wall box section, a foot of 1 " by 1 " by 1/8" wall box section, a foot of tube or pipe that will sleeve over the tube you want to bend, some " plate and something about 6 feet long to make a handle out of as well as various other odds and sods.

The first step is to cut out the "fences" for the former. These are scythe shaped with an inner radius to match the drum's outer radius (mine had a 96mm radius) and a thickness of the outside diameter of the tube you're planning on bending. The "handle" of the scythe is where the stirrup goes that pulls the tube around with the former and it wants to be roughly the diameter of the tube again higher than the fence. A decent quality jigsaw will make a reasonable job of this. If you're building a former for 1 1/8" or 1 " tube the "scythe" nearest the back of the drum will need to take into account the lip of the drum.


Fig.3
One of the "scythes" positioned on the hub





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